On the percentage of lightning flashes that begin with initial breakdown pulses (original) (raw)
Related papers
Journal of Geophysical Research, 2008
1] In this study, we identify and examine electric field pulse trains that are characteristic of preliminary breakdown in negative cloud-to-ground discharges but are not followed by return stroke waveforms. We assume that such trains are manifestations of the initiation of downward negative stepped leaders that fail to propagate all the way to the ground and refer to these events as ''attempted first cloud-to-ground leaders,'' although some of them were followed by full-fledged cloud discharges. We examined a total of 2475 electric field records of lightning events acquired in Gainesville, Florida, in 2006, and waveforms in 33 of them were found to satisfy criteria set for attempted cloud-to-ground leaders. In addition to pronounced bipolar pulses with positive (atmospheric electricity sign convention) initial half cycle, negative unipolar and negative (initial half cycle) bipolar pulses were sometimes seen toward the end of the train. We also observed that at the beginning and at the end of the pulse train, there were narrower pulses, often having durations in the range of 1-2 ms, which are more than an order of magnitude shorter than for ''classical'' preliminary breakdown pulses. The arithmetic mean of total pulse train durations is 2.7 ms, and the weighted arithmetic means of individual pulse durations and interpulse intervals are 17 and 73 ms, respectively. Some of the attempted cloud-to-ground leaders, which should belong to the cloud discharge category, can be misclassified as negative cloud-to-ground discharges by lightning locating systems such as the U.S. National Lightning Detection Network.
2014
This is the new study of the electric field changes generated by the preliminary 10 breakdown for positive cloud-to-ground flashes which concerning on the association of 11 slow field changes in preliminary breakdown process. In this study, a 107 positive cloud-12 to-ground lightning flashes recorded from the total of 14 thunderstorms generated by the 13 whole flash were examined. The electric fields were measured with nanosecond 14 resolution by using the slow electric field, fast electric field and narrowband radiation 15 field at 3 and 30 MHz signals simultaneously. Our result shows that there is a pre-starting 16 time, i.e. the duration between the first preliminary breakdown pulse and slow field 17 changes starting point, which is found to be after the first preliminary breakdown pulse.
Atmosphere, 2016
This paper presents the characteristics of the preliminary breakdown pulses (PBP) in 51 positive ground flashes recorded during 2014 summer thunderstorms in Sweden. Electric field measurements were conducted remotely using a broadband antenna system (up to 100 MHz) for a recording length of 1 s with 200 ms trigger time. In the analysis, PBP trains were observed in 86% of the cases. Based on the number of trains preceding the first return stroke, the PBP were classified into single and multiple train PBP. Characteristics of the first PBP train were determined and based on the initial polarity of the pulses, three types of PBP were identified. Characteristics of the subsequent PBP trains in the multiple train PBP were also analyzed and they were compared with the first PBP train. Based on the conceptual charge cloud configuration, we found that the inverted dipole is consistent with our observation. We also found that PBP in positive ground flashes during summer thunderstorms in Sweden are weak since the average ratios of the PBP peak to the first return stroke peak lie only between 0.21 and 0.26. Possible reasons for no detection of PBP and the different types of PBP observed were also discussed.
Journal of Atmospheric and Solar-Terrestrial Physics, 2012
This is the new study of the electric field changes generated by the preliminary 10 breakdown for positive cloud-to-ground flashes which concerning on the association of 11 slow field changes in preliminary breakdown process. In this study, a 107 positive cloud-12 to-ground lightning flashes recorded from the total of 14 thunderstorms generated by the 13 whole flash were examined. The electric fields were measured with nanosecond 14 resolution by using the slow electric field, fast electric field and narrowband radiation 15 field at 3 and 30 MHz signals simultaneously. Our result shows that there is a pre-starting 16 time, i.e. the duration between the first preliminary breakdown pulse and slow field 17 changes starting point, which is found to be after the first preliminary breakdown pulse.
Parameters of triggered-lightning flashes in Florida and Alabama
Journal of Geophysical Research, 1993
Channel base currents from triggered lightning were measured at the NASA Kennedy Space Center, Florida, during summer 1990 and at Fort McClellan, Alabama, during summer 1991. Additionally, 16-mm cinematic records with 3-or 5-ms resolution were obtained for all flashes, and streak camera records were obtained for three of the Florida flashes. The 17 flashes analyzed here contained 69 strokes, all lowering negative charge from cloud to ground. Statistics on interstroke interval, no-current interstroke interval, total stroke duration, total stroke charge, total stroke action integral ($ i 2dt), return stroke current wave front characteristics, time to half peak value, and return stroke peak current are presented. Return stroke current pulses, characterized by rise times of the order of a few microseconds or less and peak values in the range of 4 to 38 kA, were found not to occur until after any preceding current at the bottom of the lightning channel fell below the noise level of less than 2 A. Current pulses associated with M components, characterized by slower rise times (typically tens to hundreds of microseconds) and peak values generally smaller than those of the return stroke pulses, occurred during established channel current flow of some tens to some hundreds of amperes. A relatively strong positive correlation was found between return stroke current average rate of rise and current peak. There was essentially no correlation between return stroke current peak and 10-90% rise time or between return stroke peak and the width of the current waveform at half of its peak value.
Cloud-to-ground lightning flash characteristics in the contiguous United States: 1989–1991
Journal of Geophysical Research, 1994
Wideband magnetic direction finders have been used to obtain a cloud-to-gro_und lightning flash count for the contiguous United States, an area of 7.7 x 10 6 km 2, for the period 1989 through 1991. Over 46 million flashes to ground were recorded and are divided among the three years, 13.4 million in 1989, 15.9 million in 1990, and 16.9 million in 1991. Maximum flash densities occur in Florida and increase each year, from 9 flashes km -2 (1989) to 13 flashes km -2 (1991). The database contains 1.7 million positive flashes divided among the three years, 0.4 million in 1989, 0.6 million in 1990, and 0.7 million in 1991. In 1990 and 1991 the positive flash density maximum occurred in Florida but elsewhere in 1989. Secondary maximum positive flash densities occur throughout the Midwest. The annual mean percentage of positive flashes in the total lightning count is 3.7% for the period 1989-1991. The interannual variation is small, ranging from 3.1% (1989) to 4.0% (1991). However, in any given year the geographical variation of the percentage of positive flashes is large. The percentage of positive flashes is 2% (1989) at the latitude of Florida but near 25% and higher at the latitudes of the upper Midwest, Maine, and Oregon.
Journal of Geophysical Research: Atmospheres
This study compared the detection capabilities of the Geostationary Lightning Mapper (GLM) and ground-based Earth Networks Total Lightning Network (ENL) over the contiguous United States (CONUS) from 25 April 2017 to 5 May 2018. GLM detection efficiency (DE) relative to ENL varied spatially with greater DE in the southeastern United States and lower DE in the Northern Plains. Regions with greater DE were often regions where most intracloud flashes had normal positive polarity, while lower DE regions frequently had inverted negative intracloud. According to the tripolar noninductive charging model, inverted intracloud flashes are lower altitude than normal intracloud flashes. This lower altitude flash may result in greater cloud scattering of the optical lightning signal, which at cloud top is less than the GLM detection limits. DE was generally also greater for greater absolute peak current flashes, which serves as a proxy for optical energy. Additionally, GLM observed flashes to be generally greater in area and duration in the eastern relative to the western CONUS, which may result in the greater DE. GLM DE was also varied with the solar zenith angle as greatest DE occurred at night. ENL DE relative to GLM was varied spatially over CONUS with greater DE over eastern CONUS. ENL DE was greater for flashes of greater GLM flash radiant energy, area, and duration. 1.1. Lightning and Electrical Charging Proper evaluation of GLM and its detection necessitates understanding the cause of lightning and lightning characteristics. Noninductive charging (NIC), resulting from collisions of ice hydrometeors in the presence of supercooled water, likely represents the primary mechanism for electrical charging and the production of lightning in storms (Saunders et al., 2006). Charging of hydrometeors can be either positive or negative, with differences in charge partially neutralized by lightning discharges after sedimentation of charged hydrometeors. Stronger updrafts in the mixed-phase region (0°C to approximately −40°C) generally produce more charging and more frequent lightning flashes that are smaller and weaker (Bruning & MacGorman, 2013; Mecikalski et al., 2015). At warmer temperatures (e.g., 0°C to −10°C), graupel hydrometeors are positively charged during riming collisions, while ice particles are negatively charged. At cooler temperatures (e.g., −20°C to −40°C), graupel charges negatively, while ice hydrometeors charge positively. Since graupel is heavier relative to ice, a lowest positive-charged layer will generally form, while negatively charged ice particles are lofted to near negatively charged graupel, forming a negatively charged layer above the lowest positively charged layer. The positively charged ice is lifted upward to form an upper layer of positive charge. This forms the typical tripolar model of charging and lightning formation (see Figure 1 of Williams (1989) for further illustration). Examination of electric field data from balloons released into 33 thunderstorms indicates that the tripolar structure is generally observed in the updraft core (Stolzenburg et al., 1998).
Journal of Geophysical Research, 1991
The frequency distribution of the peak signal strength associated with the first detected return stroke of positive and negative cloud-to-ground flashes was studied using lightning data from northeastern Colorado. These data were obtained during 1985 with a network of medium-high gain direction finders (DFs) having a nominal range of 300 km. The median normalized signal strength of positive flashes was almost 2 times that of the negatives for flashes within 300 km of the DFs (170 versus 96 Lightning Location and Protection, Inc. (LLP), units). These DFs have an inherent detection threshold bias that tends to discriminate against weak signals. This bias increases with range and affects the detection of positive and negative flashes in different ways because of the differing character of their distributions. Positive flashes appear to have a large percentage (12 times larger than that of negative flashes) of signals clustered around very weak values (below 30 units) that are lost to the Colorado detection system of medium-high gain very quickly with increasing range (most of these are undetected by 125 km). The resulting median for positive signals thus could appear to be much larger than the median for negative signals, which are more clustered around intermediate values (80 units). When only flashes very close (20-60 km) to the DFs are considered, however, the two distributions have almost identical medians (70 units). The large percentage of weak positive signals (below 30 units) detected close to the DFs (about 10 times larger than that of negative signals) has not been previously explored. It has been suggested that they come from intracloud discharges and are improperly classified as coming from CG flashes. The evidence in hand, however, points to their being real positive, albeit weak, cloud-toground flashes. Whether or not they are real positive ground flashes, it is important to be aware of their presence in data from magnetic DF networks. Even if the weak positive signals are eliminated by considering only distant flashes (beyond about 125 km), the frequency distributions of positive and negative signal strengths are very different, the positives lacking the large percentage of intermediate signals (around 80 units) of the negatives but having a somewhat larger relative frequency of large and very large signals (beyond 130 units). 22,307 22,308 L6PEZ ET AL.: SIGNAL STRENGTH OF CLOUD-TO-GROUND LIGHTNING ß . ß ß ß ß " Negative (82,059) ß .; ß ß Negative (26,834) ., ß ., ß ß ß ß ß ß ....'" Positive ß (659) ß © ß e e e e ß e ß e eeeeeeee __ e e e e ß ... •e•ative$ _ ß ß e ß ©ee e e e ß ee ß -ß eeeee ee ß ß e ee ß ß e
Electromagnetic activity before initial breakdown pulses of lightning
Journal of Geophysical Research: Atmospheres, 2014
Lightning flash initiation is studied using electric field change (E‐change) measurements made in Florida. An initial E‐change (IEC) was found immediately before the first initial breakdown (IB) pulse in both cloud‐to‐ground (CG) and intracloud (IC) flashes if the E‐change sensor was within 80% of the reversal distance of the IEC. For 18 CG flashes, the IECs had an average point dipole moment of 23 C m and an average duration of 0.18 ms; these parameters for 18 IC flashes were −170 C m and 1.53 ms. The IECs of CG flashes began with a change in the slope of the E‐change (with respect to time) from zero slope to a positive slope, consistent with downward motion of negative charge and/or upward motion of positive charge. For IECs of IC flashes, the beginning slope change was from zero to negative slope, consistent with upward motion of negative charge and/or downward motion of positive charge. During an IEC, the E‐change monotonically increased for CG flashes and monotonically decrease...
International Journal on Electrical Engineering and Informatics
Positive lightning can do more damage than negative lightning. We have observed 77 positive cloud to ground (CG) flashes preceded by preliminary breakdown (PB) in Padang, Indonesia. It was found that there were two types of polarity between the PB pulse train and the following first return stroke (RS) pulses, namely the same polarity (type S) and composite polarity (type C). The occurence percentages of type S and type C were 92.2% and 7.8%, respectively. The aritmathic mean (AM) and geometric mean (GM) PB/RS separations and durations were 97.31 ms, 76.33 ms and 98.15 ms, 77.49 ms, respectively. The AM and GM PB/RS ratios were 12.26% and 10.20%, respectively. In addition, the characteristics of the PB pulse such as individual pulse duration, pulse train duration, and interpulse duration are discussed in this paper.